A Large Dynamic Range Reconfigurable Interpolation Digital Transmitter for NB-IoT Applications

In this letter, we present a digital transmitter for dual-band narrowband-Internet-of-Things (NB-IoT) applications achieving a large dynamic range with high-speed cartesian RF-DACs requiring less area and consuming low power consumption. The proposed transmitter incorporates integrated output baluns, a reconfigurable digital interpolater-based oversampling for DAC image suppression, or avoidance of coexistence channel. A true SAW-less design is realized by external low-cost low-pass filtering of the spurious emission satisfying NB-IoT requirements. Implemented in standard 40-nm CMOS technology with a core area of $2.1\times1.5$ mm ² and packaged with QFN-68, the transmitter achieves a dynamic range from −47.5 to 24.8 dBm with error vector magnitude (EVM) <−25 dB. The peak efficiency is 44.1% at 28.7-dBm output power, with a 2.4-V power supply.